Development of Detailed Kinetic Models for Fischer-Tropsch Fuels

Conference · Tue Oct 28 04:00:00 EDT 2008

OSTI ID:951512

Westbrook, C K; Pitz, W J; Carstensen, H; Dean, A M

Fischer-Tropsch (FT) fuels can be synthesized from a syngas stream generated by the gasification of biomass. As such they have the potential to be a renewable hydrocarbon fuel with many desirable properties. However, both the chemical and physical properties are somewhat different from the petroleum-based hydrocarbons that they might replace, and it is important to account for such differences when considering using them as replacements for conventional fuels in devices such as diesel engines and gas turbines. FT fuels generally contain iso-alkanes with one or two substituted methyl groups to meet the pour-point specifications. Although models have been developed for smaller branched alkanes such as isooctane, additional efforts are required to properly capture the kinetics of the larger branched alkanes. Recently, Westbrook et al. developed a chemical kinetic model that can be used to represent the entire series of n-alkanes from C{sub 1} to C{sub 16} (Figure 1). In the current work, the model is extended to treat 2,2,4,4,6,8,8-heptamethylnonane (HMN), a large iso-alkane. The same reaction rate rules used in the iso-octane mechanism were incorporated in the HMN mechanism. Both high and low temperature chemistry was included so that the chemical kinetic model would be applicable to advanced internal combustion engines using low temperature combustion strategies. The chemical kinetic model consists of 1114 species and 4468 reactions. Concurrently with this effort, work is underway to improve the details of specific reaction classes in the mechanism, guided by high-level electronic structure calculations. Attention is focused upon development of accurate rate rules for abstraction of the tertiary hydrogens present in branched alkanes and properly accounting for the pressure dependence of the ?-scission, isomerization, and R + O{sub 2} reactions.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 951512
• Report Number(s): LLNL-CONF-408237
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
09 BIOMASS FUELS
30 DIRECT ENERGY CONVERSION
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALKANES
BIOMASS
CHEMISTRY
COMBUSTION
DIESEL ENGINES
ELECTRONIC STRUCTURE
GAS TURBINES
GASIFICATION
HYDROCARBONS
INTERNAL COMBUSTION ENGINES
ISOMERIZATION
KINETICS
PHYSICAL PROPERTIES
POUR POINT
PRESSURE DEPENDENCE
REACTION KINETICS
SPECIFICATIONS